[BirdOPrey5]

There's no condition specifically for 2nd posts but if you set your forum to a set number of posts per page you could make a condition like:

<vb:if condition="$post[postcount] == 2 OR $post[postcount] == 12  OR$post[postcount] == 22 OR $post[postcount] == 32 OR $post[postcount] == 42 OR $post[postcount] == 52 OR $post[postcount] == 62">
</vb:if>

...and so on... Assuming 10 posts per page- Yeah at some point the condition won't work anymore but how many threads really go X number of pages anyway. I assume you want it to show an ad so if it works in 95% of thread pages it should be good enough.

Otherwise I'd imagine a plugin could be written to keep count and be true only for 2nd posts.